Field of Endeavor
The present invention relates to light water reactor spent fuel assemblies, and more particularly Pressurized Water Reactor (PWR) spent fuel assemblies with both UO2 and mixed oxide (MOX) types of fuel and more particularly to determining whether fuel rods (pins) within PWR spent fuel assemblies are missing or have been replaced with dummy fuel rods.
State of Technology
U.S. Pat. No. 7,514,695 for a detector and method for inspecting a sealed nuclear storage container provides the following state of technology information: “Heretofore, spent nuclear fuel has been placed in fuel storage casks which are typically stored above ground, at various locations in the continental United States. These storage areas are typically in restricted areas, and security is provided to protect the casks from possible tampering or the removal of any spent nuclear fuel. At present, the only indication of possible reactor spent fuel diversion from a storage cask is provided by means of tamper-indicating tags and seals which are provided with each of the storage casks. With the increasing risk of terrorist acts within the United States, and the possibility that spent nuclear fuel sources might by sought after and diverted for possible terrorist acts, a renewed effort has been undertaken to identify means by which spent nuclear fuel storage casks may be readily inspected to determine whether spent nuclear fuel which has been stored within same has been removed improperly from the storage cask.”
U.S. Pat. No. 4,389,568 for a method for monitoring irradiated nuclear fuel using Cerenkov radiation provides the following state of technology information: “A method is provided for monitoring irradiated nuclear fuel inventories located in a water-filled storage pond wherein the intensity of the Cerenkov radiation emitted from the water in the vicinity of the nuclear fuel is measured. This intensity is then compared with the expected intensity for nuclear fuel having a corresponding degree of irradiation exposure and time period after removal from a reactor core. Where the nuclear fuel inventory is located in an assembly having fuel pins or rods with intervening voids, the Cerenkov light intensity measurement is taken at selected bright spots corresponding to the water-filled interstices of the assembly in the water storage, the water-filled interstices acting as Cerenkov light channels so as to reduce cross-talk. On-line digital analysis of an analog video signal is possible, or video tapes may be used for later measurement using a video editor and an electrometer. Direct measurement of the Cerenkov radiation intensity also is possible using spot photometers pointed at the assembly.”
U.S. Pat. No. 4,335,466 for a method and apparatus for measuring irradiated fuel profiles provides the following state of technology information: “In order to comply with various safeguards agreements, inspection organizations such as NRC (Nuclear Regulatory Commission) and IAEA (International Atomic Energy Agency) need a capability of very quickly and accurately monitoring in a non-destructive manner the fissile content of spent fuel assemblies in storage pools. Presently, measurements of the content of residual and produced fissile material are not directly measured but rather are inferred by measuring particular data which is correlated to burnup (which is a measure of nuclear reactor fuel consumption, expressed either as a percent of fuel atoms that have undergone fission or as the amount of energy produced per unit weight of fuel).”